Everyone knows that exercise is a good thing. But when New York Times science reporter Kolata (Flu) set out to investigate the claims of various fitness regimens, she found that "the tiny pearls of good science are buried in mountains of junk." Much of the accepted wisdom about exercise, it turns out, is false-from the belief that endorphins cause an exertion-induced euphoria to the notion that all individuals, with sufficient effort, can become fit. An avid devotee of "spinning," a type of stationary biking that mimics actual road conditions, Kolata brings both personal enthusiasm and journalistic skepticism to her subject. She traces the history of the fitness movement from the ancient Greeks through the 18th and early 19th centuries, when feats of strength and endurance became a popular means of entertainment. By the 20th century, increasingly sedentary living prompted a new interest in fitness: the jogging fad emerged in the 1970s, followed by aerobics, weight lifting and other activities. Kolata looks at hard data about exercise, but also interviews enthusiasts and promoters, whose devotion to their regimens sometimes transcends the available facts. People exercise for different reasons, Kolata finds. For improving overall health, moderate exercise appears to be sufficient. To improve physical appearance, intense effort is required. To reach a sense of exhilaration and strength, however, one must actually love physical exertion for its own sake. The "truth" about exercise, Kolata concludes, may lie in the view of psychopharmacologist Richard Friedman, who suggests that "exercise is more often a marker of health than its cause." Illus. not seen by PW. Agent, John Brockman. (May) Forecast: Kolata's many readers will clamor for this newest title-and marketing will reach beyond them. Copyright 2003 Reed Business Information. -- PUBLISHERS WEEKLY.